Amtrak trains began rolling on the busy Northeast Corridor early Monday, the first time in almost a week following a deadly crash in Philadelphia, and officials vowed to have safer trains and tracks while investigators worked to determine the cause of the derailment.

Amtrak resumed service along the corridor with a 5:30 a.m. southbound train leaving New York City. The first northbound train, scheduled to leave Philadelphia at 5:53 a.m., was delayed and pulled out of 30th Street Station at 6:07 a.m.

About three dozen passengers boarded the New York City-bound train in Philadelphia, and Mayor Michael Nutter was on hard to see the passengers and train off.

All Acela Express, Northeast Regional and other services were to also resume.

Amtrak officials said Sunday that trains along the Northeast Corridor from Washington to Boston would resume service in "complete compliance" with federal safety orders following last week's deadly derailment.

Company President Joseph Boardman said Amtrak staff and crew have been working around the clock to restore service following Tuesday night's crash that killed eight people and injured more than 200 others.

Boardman said Sunday that Amtrak would be offering a "safer service."

In Philadelphia on Monday, Nutter stood on the platform, greeting passengers and crew members. He pulled out his cellphone and took pictures as the train rolled out just after 6 am.

"It's great to be back," said Christian Milton of Philadelphia. "I've never had any real problems with Amtrak. I've been traveling it for over 10 years. There's one accident in 10 years. Something invariably is going to happen somewhere along the lines. I'm not worried about it."

Milton said he'd probably be sleeping as the train goes around the curve where the derailment happened. But, he said he'll think about victims.

"I might say a prayer for the people who died and got injured," he said.

Tom Carberry, of Philadelphia, praised the agencies involved in restoring service.

"My biggest takeaway was the under-promise and over-deliver and the surprise of having it come back this morning when that wasn't expected," Carberry said. "That was a good thing for Amtrak."

At New York City's Penn Station early Monday, police with a pair of dogs flanked the escalator as a smattering of passengers showed their tickets to a broadly smiling Amtrak agent and headed down to the platform.

A sign outside the train flashed "All Aboard" in red letters.

The conductor gave a broad all-clear wave, stepped inside and the train glided out of the station at 5:30 a.m.

Passenger Raphael Kelly of New York, looking relaxed, said he was "feeling fine" and had "no worries."

Kelly, who takes Amtrak to Philadelphia weekly, said with a smile that if he did have any concerns, "I have to get over it."

Kelly said that if anything, the train might be safer than ever.

"They're on their toes" because of the crash, he said.

At a service Sunday evening at the site to honor the crash victims, Boardman choked up as he called Tuesday "the worst day for me as a transportation professional." He vowed that the wrecked train and its passengers "will never be forgotten.

Federal regulators on Saturday ordered Amtrak to expand use of a speed-control system long in effect for southbound trains near the crash site to northbound trains in the same area.

Federal Railroad Administration spokesman Kevin Thompson said Sunday the automatic train control system is now fully operational on the northbound tracks. Trains going through that section of track will be governed by the system, which alerts engineers to slow down when their trains go too fast and automatically applies the brakes if the train continues to speed.

The agency also ordered Amtrak to examine all curves along the Northeast Corridor and determine if more can be done to improve safety, and to add more speed limit signs along the route.